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The number of participants in the AMB-220-E analysis set who experienced AEs (including serious AEs) of severe severity (ie, made it impossible to perform routine activities and the subject may have experienced intolerable discomfort or pain) that began after entering AMB-220-E (treatment-emergent AEs) and that occurred in more than 1 participant are summarized by dose group. The AMB-220-E analysis set consisted of all participants who received at least 1 dose of study drug during the AMB-220-E study.

Number of Participants With PAH Who Completed the Phase II NCT00046319 Study and Who Experienced AEs of Moderate Severity During Long-term Ambrisentan Exposure [ Time Frame: Week 24 (AMB-220-E baseline) to Week 329.3 ]

The number of participants in the AMB-220-E analysis set who experienced AEs (including serious AEs) of moderate severity (ie, interfered with routine activities and subject may have experienced significant discomfort) that began after entering AMB-220-E (treatment-emergent AEs) and that occurred in more than 1 participant are summarized by dose group. The AMB-220-E analysis set consisted of all participants who received at least 1 dose of study drug during the AMB-220-E study.

Number of Participants With PAH Who Completed the Phase II NCT00046319 Study and Who Experienced AEs of Mild Severity During Long-term Ambrisentan Exposure [ Time Frame: Week 24 (AMB-220-E baseline) to Week 329.3 ]

The number of participants in the AMB-220-E analysis set who experienced AEs (including serious AEs) of mild severity (ie, did not interfere with routine activities and the subject may have experienced slight discomfort) that began after entering AMB-220-E (treatment-emergent AEs) and that occurred in more than 1 participant are summarized by dose group. The AMB-220-E analysis set consisted of all participants who received at least 1 dose of study drug during the AMB-220-E study.

The 6MWT was conducted according to the American Thoracic Society guidelines (ATS statement: guidelines for the six-minute walk test. Am J Respir Crit Care Med 2002; 166(1):111-117.) Primary efficacy analyses were performed for the AMB-220-E analysis set (all subjects who received at least 1 dose of study drug during the AMB-220-E study).

The 6MWT was conducted according to the American Thoracic Society guidelines (ATS statement: guidelines for the six-minute walk test. Am J Respir Crit Care Med 2002; 166(1):111-117.) Primary efficacy analyses were performed for the AMB-220-E analysis set (all subjects who received at least 1 dose of study drug during the AMB-220-E study).

The 6MWT was conducted according to the American Thoracic Society guidelines (ATS statement: guidelines for the six-minute walk test. Am J Respir Crit Care Med 2002; 166(1):111-117.) Primary efficacy analyses were performed for the AMB-220-E analysis set (all subjects who received at least 1 dose of study drug during the AMB-220-E study).

The 6MWT was conducted according to the American Thoracic Society guidelines (ATS statement: guidelines for the six-minute walk test. Am J Respir Crit Care Med 2002; 166(1):111-117.) Primary efficacy analyses were performed for the AMB-220-E analysis set (all subjects who received at least 1 dose of study drug during the AMB-220-E study).

The 6MWT was conducted according to the American Thoracic Society guidelines (ATS statement: guidelines for the six-minute walk test. Am J Respir Crit Care Med 2002; 166(1):111-117.) Primary efficacy analyses were performed for the AMB-220-E analysis set (all subjects who received at least 1 dose of study drug during the AMB-220-E study).

Change from baseline evaluated after 24 (baseline), 48, 108, 156, and 204 weeks of ambrisentan therapy in BDI (measured as units on a scale) immediately following exercise. Borg Dyspnea Index, a measure of perceived shortness of breath: 0 units on a scale (none) to 10 units on a scale (maximum breathlessness).

Change from baseline evaluated after 24 (baseline), 48, 108, 156, and 204 weeks of ambrisentan therapy in BDI (measured as units on a scale) immediately following exercise. Borg Dyspnea Index, a measure of perceived shortness of breath: 0 units on a scale (none) to 10 units on a scale (maximum breathlessness).

Change from baseline evaluated after 24 (baseline), 48, 108, 156, and 204 weeks of ambrisentan therapy in BDI (measured as units on a scale) immediately following exercise. Borg Dyspnea Index, a measure of perceived shortness of breath: 0 units on a scale (none) to 10 units on a scale (maximum breathlessness).

Change from baseline evaluated after 24 (baseline), 48, 108, 156, and 204 weeks of ambrisentan therapy in BDI (measured as units on a scale) immediately following exercise. Borg Dyspnea Index, a measure of perceived shortness of breath: 0 units on a scale (none) to 10 units on a scale (maximum breathlessness).

Change from baseline evaluated after 24 (baseline), 48, 108, 156, and 204 weeks of ambrisentan therapy in BDI (measured as units on a scale) immediately following exercise. Borg Dyspnea Index, a measure of perceived shortness of breath: 0 units on a scale (none) to 10 units on a scale (maximum breathlessness).

The SGA was determined using a visual-analog scale. Subjects were asked the question, "How are you feeling today?" and were asked to draw a vertical mark on a 100-mm horizontal line in which zero represented "very poor" and 100 represented "excellent."

The SGA was determined using a visual-analog scale. Subjects were asked the question, "How are you feeling today?" and were asked to draw a vertical mark on a 100-mm horizontal line in which zero represented "very poor" and 100 represented "excellent."

The SGA was determined using a visual-analog scale. Subjects were asked the question, "How are you feeling today?" and were asked to draw a vertical mark on a 100-mm horizontal line in which zero represented "very poor" and 100 represented "excellent."

The SGA was determined using a visual-analog scale. Subjects were asked the question, "How are you feeling today?" and were asked to draw a vertical mark on a 100-mm horizontal line in which zero represented "very poor" and 100 represented "excellent."

The SGA was determined using a visual-analog scale. Subjects were asked the question, "How are you feeling today?" and were asked to draw a vertical mark on a 100-mm horizontal line in which zero represented "very poor" and 100 represented "excellent."

Clinical worsening of PAH was defined as death, lung transplantation, hospitalization for PAH, atrial septostomy, the addition of approved prostanoid therapy, or study withdrawal due to the addition of other clinically approved PAH therapeutic agents. Sildenafil, a type 5 phosphodiesterase (PDE-5) inhibitor, had not received regulatory approval for the treatment of PAH until late in the conduct of AMB 220 and AMB 220-E, and did not count toward clinical worsening. Results are presented as the Kaplan-Meier estimate (% probability) of not having clinical worsening after a given time.

Failure-free treatment status was defined as the time from initiation of active treatment to the first occurrence of death, lung transplantation, the addition of approved prostanoid therapy, or study withdrawal due to the addition of other clinically approved PAH therapeutic agents. Results are presented as the Kaplan-Meier estimate (% probability) of not having treatment failure after a given time.

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Ages Eligible for Study:

18 Years and older (Adult, Senior)

Sexes Eligible for Study:

All

Accepts Healthy Volunteers:

No

Criteria

Inclusion Criteria:

Must have completed Visit 14/Week 24 of the NCT00046319 study.

Women of childbearing potential must have a negative urine pregnancy test at the Screening/Enrollment Visit and agree to use a reliable double barrier method of contraception until study completion and for >=4 weeks following their final study visit.

Must have completed the Down-titration Period of NCT00046319 prior to enrollment in AMB-220-E and will meet the following additional criteria:

Subjects with a diagnosis of HIV must have stable disease status at the time of Screening/Enrollment.

Must be stable on conventional therapy for PAH for >=4 weeks prior to the Screening Visit.

Exclusion Criteria:

Chronic prostanoid therapy, or other investigational prostacyclin derivative within 4 weeks prior to the Screening Visit.

Intravenous inotrope use within 2 weeks prior to the Screening Visit.

Females who are pregnant or breastfeeding.

Contraindication to treatment with an endothelin receptor antagonist (ERA).